Photoacoustic assay and imaging system

Abstract

A method for assaying a component of a localized region of interest in a body comprising: illuminating the region with at least one pulse of radiation having a wavelength at which the radiation is absorbed by the component to generate a change in an acoustic property of the region; transmitting ultrasound so that it is incident on the region; measuring at least one effect of the change on the incident ultrasound; using the measured at least one effect to determine an absorption coefficient for the radiation in the region; and using the determined absorption coefficient to determine concentration of the component in the region.

Description

RELATED APPLICATIONSThe present application claims priority under 35 U.S.C. §120 to Israel Patent Application No. 138073, which was filed on Aug. 24, 2000.FIELD OF THE INVENTIONThe invention relates to non-invasive in-vivo methods and apparatus for determining the concentration of a substance in a body and for determining the concentration of the substance as a function of position in the body.BACKGROUND OF THE INVENTIONMethods and apparatus for in-vivo and in-vitro measurements of blood glucose levels are known in the art. Generally, the methods and apparatus are relatively complicated and measurements of a person's blood glucose levels are usually performed in a clinic or laboratory with the aid of a technician and costs of the measurements are relatively high.Methods and apparatus for determining blood glucose levels for use in the home, for example by a diabetic who must monitor blood glucose levels frequently, are available. These methods and associated devices are generally in...

AI Technical Summary

Benefits of technology

An aspect of some embodiments of the present invention relates to providing a non-invasive, in-vivo glucometer that determines a person's glucose level substantially only from glucose concentration in the person's blood.

In some embodiments of the present invention transit time of ultrasound through the bolus is determined from a pulse of ultrasound energy that repeatedly “bounces” back and forth between walls of a blood vessel in which the bolus is located before the energy exits the blood vessel and the bolus. As a result, the ultrasound energy traverses the bolus a plurality of times and speed of sound in the bolus is determined from a transit time of the acoustic energy pulse through the bolus over a path length many times a characteristic dimension of the bolus. Accuracy of a determination of the speed of sound generally increases as the path length over which the transit time is measured increases. A speed of sound in blood determined from a pulse of ultrasonic energy that traverses the bolus a plurality of times is therefore relatively more accurate than a speed of sound determined from a pulse of ultrasound energy that traverses the bolus once.

In should be noted that passing an ultrasound pulse through a blood bolus a plurality of times, in accordance with an embodiment of the present invention, can also be used to provide accurate measurements of other changes in the blood bolus caused by absorption of energy from the at least one light pulse. For example, “multipass measurements” can be used to acquire accurate measurements of changes in the absorption coefficient in blood for ultrasound.

Problems solved by technology

Generally, the methods and apparatus are relatively complicated and measurements of a person's blood glucose levels are usually performed in a clinic or laboratory with the aid of a technician and costs of the measurements are relatively high.

These methods and associated devices are generally invasive and usually involve taking blood samples by finger pricking.

Finger pricking is perceived as inconvenient and unpleasant and to avoid finger pricking diabetics tend to monitor their glucose levels less frequently than is advisable.

Moreover, many conventional glucometers require routine purchasing of sample sticks and pricking needles, which is bothersome and adds cost to the user.

However, light is scattered by body tissue and even though the light is focused to a small focal region inside the body, the location and size of the absorbing tissue region are not accurately known.

Measurements of blood glucose levels can therefore be affected by unknown variables that substantially compromise the reliability of the measurements.

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